1. Field of the Invention
The present invention concerns a soundproof lining for a gas pipe. It also concerns tools for fabricating elements of this lining.
The invention's lining, because of its thinness, lightness, good impact resistance and ease of installation, is particularly suitable for soundproofing the upstream and downstream housings of a turbojet fan. Generally speaking, it can be used advantageously whenever it is necessary to reduce the noise level produced in a large-diameter stream by a gas flow with a relatively low temperature.
2. Description of the Prior Art
The lining of the invention is of the type consisting of the juxtaposition of composite soundproofing panels within which are resonant cavities which communicate with the gas flow by a multiplicity of vents. Such composite panels are already known, in particular through the French Pat. No. 2 201 010. They include two sheets facing one another, one of which, in contact with the gas flow, is perforated. These two sheets are braced by a corrugated sheet, the corrugations of which delimit the resonant cavities. The three sheets are of metal and are rigidly assembled by brazing. Such composite panels must have precise radii of curvature since their rigidity makes it impossible to compensate for size defects by deformation during assembly. This rigidity is even more bothersome when the gas flow stream is large-sectioned. The wall of the stream itself has curve defects. The problem can be solved by interposing a mattress of a flexible and porous material, as has already been proposed in the French Pat. No. 2 396 868. But this solution is only suitable for relatively small-sectioned streams. Otherwise the lining becomes too cumbersome and heavy.